Mechanism of Radial Stress in the Freezing Direction Produced by Non-Frost-Susceptible Materials

Abstract

Radial stress produced by the freezing of soil mainly results from two parts: the segregated ice lens and the in situ freezing of pore water. However, most studies concentrate on the stress of freezing direction, but little known about radial stress. In this study, a series of freezing experiments were conducted by a novel designed frost heave cell, which can provide strong radial constraint to reduce the possible uneven deformation in the radial direction. To distinguish the contribution of in situ freezing from segregated ice lenses to the radial stress, the authors adopted three different non-frost-susceptible materials (Toyoura standard sand, washed sand, and 0.1 mm glass beads) and agar as the experimental samples. Next, the authors compared the radial stresses produced by the freezing experiments of these four different materials with that of frost-susceptible material. In order to clarify the influence of unfrozen water content on radial stress, the authors adopted an improved pulse nuclear magnetic resonance method to measure the unfrozen water content at negative temperatures for these four different materials. In comparison with other research concerning the freezing stress of sand, it is concluded that in situ freezing of non-frost-susceptible materials produces isotropic stress in freezing and its radial direction. The sizes and surface conditions of particles are considered as the main factors that affect the maximum value of radial stress. The reduction process of unfrozen water affects the increasing curve of the radial stress of agar during freezing.